VCSELs have recently generated considerable interest, due to their potential for high output power and spatial coherence. See, for instance, R. A. Morgan et al., Applied Physics Letters, Vol. 61, p. 1160 (1992). The spatial coherence typically is required for applications that involve beam focusing (e.g., pump laser for a fiber amplifier) and/or beam steering.
Beam focusing is a frequently present feature of articles that comprise a semiconductor laser which, up to now, has required provision of an appropriate separate focusing element, typically a lens. This is an obvious disadvantage, entailing additional cost and complexity, including an alignment step. Thus, it would be desirable to have available a semiconductor laser having a focused output. This application discloses such a laser, to be referred to as a "zone" laser or "Z-laser".